ps：灵活运用 Ctrl + F 进行题目查找

ps2：第 1-2 章小测，40个题里边有1个错的；第 2 次阶段测试，40个题里边有4个错的。sorry啦，太多了没时间找了。。当时测验不显示正确答案也不显示哪个错了/(ㄒoㄒ)/~~ 如果发现错误的童靴非常感谢能在评论区反馈！！

ps4：期末考试题只提供题目，部分答案可在历年考试题中找到。

ps5：平时测验、期末考试真题、考试题库等更多文件资源请从此获取：Gabriel-1023/Basement/tree/main/计算机网络

点击下方目录直接跳转

第 1-4 学时测验

  1. What type of network must a home user access in order to do online shopping?

    the Internet

  2. Which area of the network would a college IT staff most likely have to redesign as a direct result of many students bringing their own tablets and smartphones to school to access school resources?

    wireless LAN

  3. Which two connection options provide an always-on, high-bandwidth Internet connection to computers in a home office? (Choose two.)

    DSL

    cable

  4. What are two functions of end devices on a network? (Choose two.)

    They originate the data that flows through the network.

    They are the interface between humans and the communication network.

  5. An employee at a branch office is creating a quote for a customer. In order to do this, the employee needs to access confidential pricing information from internal servers at the Head Office. What type of network would the employee access?

    an intranet

第 5-8 学时测验

  1. What process is used to place one message inside another message for transfer from the source to the destination?

    encapsulation

  2. What is an advantage of network devices using open standard protocols?

    A client host and a server running different operating systems can successfully exchange data.

  3. What is indicated by the term throughput?

    the measure of the bits transferred across the media over a given period of time

  4. Which method of data transfer allows information to be sent and received at the same time?

    full duplex

  5. What is the function of the CRC value that is found in the FCS field of a frame?

    to verify the integrity of the received frame

第 9-12 学时测验

  1. What statement describes a characteristic of MAC addresses?

    They must be globally unique.

  2. Which destination address is used in an ARP request frame?

    FF-FF-FF-FF-FF-FF

  3. What addressing information is recorded by a switch to build its MAC address table?

    the source Layer 2 address of incoming frames

  4. The ARP table in a switch maps which two types of address together?

    Layer 3 address to a Layer 2 address

  5. What are the two sizes (minimum and maximum) of an Ethernet frame? (Choose two.)

    64 bytes

    1518 bytes

第 1-2 章小测

请注意阅读文章开头ps2

  1. Suppose there is exactly one packet switch between a sending host and a receiving host. The transmission rates between the sending host and the switch and between the switch and the receiving host are R1 and R2, respectively. Assuming that the switch uses store-and-forward packet switching, what is the total end-to-end delay to send a packet of length L? (Ignore queuing delay, propagation delay, and processing delay.) ( )

    A. L/R1＋L/R2

  2. In data link-layer, which protocol is used to share bandwidth? ( )

    D. CSMA/CD

  3. The ability to determine whether a frame should be forwarded to some interface or should just be dropped is ( ).

    C. filtering

  4. Which of the following is correct? ( )

    D. All of the above

  5. In ( ) transmission(s), the nodes at both ends of a link may transmit packets at the same time.

    D. full-duplex

  6. Which kind of media is a guided media? ( )

    C. fiber optics

  7. Which of the following services can not offered by a link-layer protocol? ( )

    D. congestion control

  8. ( ) means that the switch must receive the entire packet before it can begin to transmit the first bit of the packet onto the outbound link.

    B. Store-and-forward transmission

  9. The units of data exchanged by a link-layer protocol are called ( ).

    C. frames

  10. The Internet’s connection-oriented service has a name, it is ( ).

    A. TCP

  11. In the following four descriptions, which one is not correct? ( )

    D. Both switches and routers are plug and play devices.

  12. In the following options, which belongs to the network core? ( )

    C. routers

  13. MAC address is ( ) bits long.

    C. 48

  14. In CSMA/CD, the adapter waits some time and then returns to sensing the channel. In the following four times, which one is impossible? ( )

    D. 1028 bit times

  15. In the Internet, end systems are connected together by ( ).

    B. communication links

  16. In the following four services, which one was be required in PPP? ( )

    D. error correction

  17. Which of the following option belongs to the circuit-switched networks? ( )

    D. both A and B

  18. What is contained in the trailer of a data-link frame?

    B. error detection

  19. The ( )field permits Ethernet to multiplex network-layer protocols.

    B. type

  20. The time required to propagate from the beginning of the link to the next router is ( ).

    D. propagation delay

  21. The Internet provides two services to its distributed applications: a connectionless unreliable service and () service.

    B. connection-oriented reliable

  22. ( ) protocol serves to coordinate the frame transmissions of the many nodes when multiple nodes share a single broadcast link.

    B. MAC

  23. There are two classes of packet-switched networks: ( ) networks and virtual-circuit

    A. datagram

  24. A switch is a( )device that acts on frame.

    D. link-layer

  25. It defines the format and the order of messages exchanged between two or more communicating entities, as well as the actions taken on the transmission and/or receipt of a message or other event. The sentence describes ( ).

    C. protocol

  26. There are two fundamental approaches to building a network core, ( ) and packet switching.

    A. circuit switching

  27. The units of data exchanged by a link-layer protocol are called ( ).

    D. Frames

  28. There are many private networks, such as many corporate and government networks, whose hosts cannot exchange messages with hosts outside of the private network. These private networks are often referred to as ( ).

    B. intranets

  29. Which device has the same collision domain? ( )

    B. Hub

  30. The ARP table in a switch maps which two types of address together?

    D. IP address to MAC address

  31. In the Ethernet frame structure, the Data field carries the ( ).

    D. IP datagram

  32. The following protocols are belonging to multiple access protocols except for ( ).

    A. routing protocols

  33. End systems access to the Internet through its ( ).

    B. ISP

  34. Consider CRC error checking approach, the four bit generator G is 1011, and suppose that the data D is 10101010, then the value of R is( ).

    A. 010

  35. An application can rely on the connection to deliver all of its data without error and in the proper order. The sentence describes ( ).

    C. reliable data transfer

  36. ( ) provides a mechanism for nodes to translate IP addresses to link-layer address.

    B. ARP

  37. Which of the following protocols is not a link-layer protocol? ( )

    C. IP

  38. A MAC address is a ( )address.

    A. link-layer

  39. Which destination address is used in an ARP request frame?

    D. FFFF.FFFF.FFFF

  40. Suppose, a is the average rate at which packets arrive at the queue, R is the transmission rate, and all packets consist of L bits, then the traffic intensity is ( ), and it should no greater than 1.

    C. La／R

第 13-16 学时测验

  1. Datagram networks and virtual-circuit networks differ in that ( ).

    datagram networks use destination addresses and virtual-circuit networks use VC. numbers to forward packets toward their destination.

  2. Which field in the IPv4 header is used to prevent a packet from traversing a network endlessly?

    Time-to-Live

  3. A message is sent to all hosts on a remote network. Which type of message is it?

    directed broadcast

  4. Consider an IP datagram of length 2500 bytes. The data link layer takes Ethernet to transfer the data. Select the correct values of the length, flag and offset in the first and last fragment. (choose two.)

    1500, 1, 0

    1020,0,185

  5. Which three IP addresses are private ? (Choose three.)

    172.16.4.4

    10.1.1.1

    192.168.5.5

第 17-20 学时测验

  1. How many bits are in an IPv6 address?

    128

  2. What is the purpose of the subnet mask in conjunction with an IP address?

    to determine the subnet to which the host belongs

  3. How many host addresses are available on the network 172.16.128.0 with a subnet mask of 255.255.254.0?

    510

  4. A DHCP server is used to assign IP addresses dynamically to the hosts on a network. The address pool is configured with 192.168.10.0/26. There are 2 printers on this network that need to use reserved static IP addresses from the pool. How many IP addresses in the pool are left to be assigned to other hosts?

    60

  5. A company has a network address of 192.168.1.64 with a subnet mask of 255.255.255.192. The company wants to create two subnetworks that would contain 10 hosts and 18 hosts respectively. Which two networks would achieve that? (Choose two.)

    192.168.1.64/27

    192.168.1.96/28

第 21-24 学时测验

  1. What is the routing metric used for RIP?

    Hop count

  2. In distance vector algorithm, each router receives distance vectors from

    only its neighbors

  3. BGP is a(n):

    Border Gateway Routing Protocol

  4. In IP address, the first few bits of multicast address are ( )

    1110

  5. OSPF is an inter-AS routing protocol, while BGP is an intra-AS routing protocol.

    错

第 25-28 学时测验

此部分测验答案由 @Jinsui Chen 提供。

  1. The similarity of TCP and UDP is that both of them are:
    transportation-layer protocols
  2. When we adopt TCP/IP data encapsulation, which of the following port number range identifies common applications？
    0-1023
  3. Various application processes of application layer interact with transmission entities via __ .
    ports
  4. Which of the following is the important feature of UDP?
    shortest latency of data transfer
  5. When calculating UDP segment checksum, a pseudo-header should be added.
    对

第 29-32 学时测验

此部分测验答案由 @Jinsui Chen 提供。

  1. In the following options, which is not bundled with the Internet’s connection-oriented service?
    guarantee of the transmission time
  2. Assume that the transport layer takes Go-Back-N protocol. The sender has sent frames 0-5, when timeout, the sender only received acknowledgments for frames 0,2 and 3. Then the sender need retransmit______frames.
    2
  3. The sequence number in TCP segment refers to______.
    the first byte of data part
  4. The reliability of TCP transfer is based on the use of __ and __ .
    acknowledgment, retransmission
  5. When calculating UDP/TCP segment checksum, a pseudo-header should be added.
    对

第 33-36 学时测验

此部分测验答案由 @Jinsui Chen 提供。

  1. The aim of involving flow control into TCP data transfer is to:
    avoid incoming data exhausting receiver's resources
  2. What is three-way-handshaking used for?
    Connection establishment in transportation layer
  3. In TCP congestion avoidance stage, the congestion window will increase:
    linearly
  4. If the status code in HTTP response message is 404, it means:
    The requested document doesn't exit on this server.
  5. The “slow start” of TCP congestion control means that the congestion window increase one per time.
    错

第 37-40 学时测验

  1. The protocol for two computers to transport files is:

    FTP

  2. The port number for the FTP control connection is:

    21

  3. Which of the following command is used to test network connectivity?

    ping

  4. FTP uses two parallel TCP connections to transfer a file, there are

    control connection and data connection

  5. Concerning the following statements about application layer protocols, which is correct?

    DNS protocol provides hostname to IP address translation.

第 2 次阶段测试

请注意阅读文章开头ps2

  1. The data field in IP datagram can carry many types of data except ____. （ ）

    MAC

  2. Because TCP only acknowledges bytes up to the first missing byte in the stream, TCP is said to provide____.

    Cumulative acknowledgements

  3. Provided α=0.125, current value of Estimated-RTT is 0.4s, Sample-RTT is 0.8s, then the new value of Estimated-RTT is ____s.

    0.45

  4. If the subnet mask is 255.255.240.0, then how many bits indicate the host address?

    12

  5. UDP socket identified by two components, they are ____.

    destination IP address and destination port numbers

  6. Which of the following services is not provided by TCP?

    Delay guarantees and bandwidth guarantees

  7. The UDP header has only four fields, they are____.

    Source port number, destination port number, length and checksum

  8. Connection setup at the transport layer involves ____.

    only the two end systems

  9. Given the IP address 202.96.104.8/20, its subnet address is ____. （ ）

    202.96.96.0

  10. Most IPV4 datagram do not contain option field, how many bytes a header has in a typical IP datagram? （ ）

    20 bytes

  11. How does the TTL changed by one each time the datagram is processed by a router?

    decrease

  12. ____ maintains connection-state in the end systems. This connection state includes receive and send buffers, congestion-control parameters, and sequence and acknowledgment number parameters.

    TCP

  13. The port number used by HTTP is ____.

    80

  14. Which of the following is not a routing protocol?

    TCP

  15. Which of the following is not a pipelining protocol.

    Rdt1.0

  16. RIP is a kind of ____ algorithm.

    Neither of A and B

  17. Services provided by transport layer include ____.

    TCP and UDP

  18. How does TCP sender perceive congestion?

    Both A and B

  19. Transport-layer protocols run in ____.

    End systems

  20. Given the IP address 202.96.104.8/20, its broadcast address is ____.

    202.96.111.255

  21. Port number’s scope is ____ to ____.

    0, 65535

  22. IPv6 increases the size of the IP address from 32bit to ____ bit.

    128

  23. Suppose one IP datagram of 5,000 bytes (20 bytes of IP header) and it must be forwarded to a link with an MTU of 1,500 bytes, the offset and flag of the second fragment in header are ____.

    185, 1

  24. Which layer provides host-to-host services?

    transport

  25. Tracerout is implemented with ____ messages.

    ICMP

  26. New version of IP----IPV6 does not allow fragment in ____?

    Host

  27. There are two states in TCP congestion control, which are ____.

    slow start and congestion avoidance

  28. A router forwards a packet by examining the value of a field in the arriving packet’s header, and then using this value to index into the router’s forwarding table, this value is?

    destination IP address

  29. The maximum amount of data that can be grabbed and placed in a segment is limited by the____.

    MTU

  30. In DV algorithm, when one node updates its distance vector, it must ____.（ ）

    send the updated routing table to its neighbors

  31. Which of following about UDP is not correct.

    It is a reliable data transfer protocol

  32. What is the name of a network-layer packet?

    datagram

  33. IPV4 has a ___ bit address?

    32

  34. Which of the following applications normally uses UDP services?

    Streaming multimedia

  35. What are the two most important network-layer functions in a datagram network?

    forwarding & routing

  36. Given that costs are assigned to various edge in the graph abstraction. In the following four descriptions, which one is not correct? （ ）

    The least cost path is not always the shortest path.

  37. The SYN segment is used for____.

    TCP connection setup

  38. The Internet’s network layer includes the following components but ____.（ ）

    Channel Partitioning Protocol

  39. UDP and TCP both have the fields except ____.

    receive window

  40. Which of the following about TCP connection is not correct?

    It is a broadcast connection

期末考试

请注意阅读文章开头ps4

  1. TCP Potpourri.

    a. Consider two TCP connections, one between Hosts A (sender) and B (receiver), and another between Hosts C (sender) and D (receiver). The RTT between A and B is half that of the RTT between C and D. Suppose that the senders’ (A’s and C’s) congestion window sizes are identical. Is their throughput (number of segments transmitted per second) the same? Explain.

    b. Now suppose that the average RTT between A and B, and C and D are identical. The RTT between A and B is constant (never varies), but the RTT between C and D varies considerably. Will the TCP timer values of the two connections differ, and if so, how are they different, and why are they different?

    c. Give one reason why TCP uses a three-way (SYN, SYNACK, ACK) handshake rather than a two-way handshake to initiate a connection.

    d. It is said that a TCP connection “probes” the network path it uses for available bandwidth. What does this mean?

    e. What does it mean when we say that TCP uses “cumulative acknowledgement”? Give two reasons why cumulative acknowledgment is advantageous over selective acknowledgment.

  2. In chapter 2, we studied a number of multiple access protocols, including TDMA, CSMA, slotted Aloha, and token passing.

    a. Suppose you were charged with putting together a large LAN to support IP telephony (only) and that multiple users may want to carry on a phone call at the same time. Recall that IP telephony digitizes and packetizes voice at a constant bit rate when a user is making an IP phone call. How well suited are these four protocols for this scenario? Provide a brief (one sentence) explanation of each answer.

    b. Now suppose you were charged with putting together a LAN to support the occasional exchange of data between nodes (in this part of this question, there is no voice traffic). That is, any individual node does not have data to send very often. How well suited are these four protocols for this scenario? Provide a brief (one sentence) explanation of each answer.

    c. Now suppose the LAN must support both voice and data and you must choose one of these multiple access strategies in order to support both applications on the same network, with the understanding that voice calls are more important than data. Which would you choose and why? How would voice and data be sent in this scenario? That is, which access protocol would you use, or adapt/modify, and why?

  3. Try to compare the main advantages and disadvantages of circuit switching and packet switching from various aspects.

  4. Describe the network architecture of the five-layer protocol, including the main functions of each layer.

  5. What are the main features of LAN? Why does LAN use broadcast communication while WAN does not?

  6. Try to compare the advantages and disadvantages of these two services, virtual circuit and datagram, from multiple aspects.

  7. (1) What does the subnet mask 255.255.255.0 mean?

    (2) The subnet numbers of a certain type A network and a certain type B network are subnet-id of 16bit and 8bit respectively. How are the subnet masks of these two networks different?

    (3) The subnet mask of a certain class B address is 255.255.240.0. What is the maximum number of hosts on each subnet?

    (4) The subnet mask of a Class A network is 255.255.0.255. Is it a valid subnet mask?

    (5) The hexadecimal representation of an IP address is C22F1481. Try to convert it to dotted decimal format. What type of IP address is this address?

    (6) Is it practical to use subnet masks for Class C networks? Why?

  8. In the lecture we list a number of different services that a link layer can potentially provide to the network layer. These services include: a) framing, b) medium access, c) reliable delivery, d) flow control, e) error detection, f) error correction, g) full-duplex and half-duplex. For each of these services, discuss how or how not Ethernet provides the service.

  9. Consider a packet of length L which begins at end system A, travels over one link to a packet switch, and travels from the packet switch over a second link to a destination end system. Let di, si and Ri denote the length, propagation speed, and transmission rate of link i, for i = 1, 2. The packet switch delays each packet by dproc. Assuming no queuing delays, in terms of di, si, Ri, (i = 1, 2) and L, what is the total end-to-end delay for the packet? Suppose the packet is 1,000 bytes, the propagation speed on both links is 2.5 * 108 m/s the transmission rates of both links is 1 Mbps, the packet switch processing delay is 1 msec, the length of the first link is 4,000 km, and the length of the last link is 1,000 km. For these values, what is the end-to-end delay?

    Suppose R1=R2=R and dproc = 0.Furthermore, suppose the packet switch does not store-and-forward packets but instead immediately transmits each bit it receives before waiting for the packet to arrive. What is the end-to-end delay?

  10. Consider sending a packet of F bits over a path of Q links. Each link transmits at R bps. The network is lightly loaded so that there are no queuing delays. Propagation delay is also negligible.

    a. Suppose the network is a packet-switched datagram network and a connection-oriented service is used. Suppose each packet has h * F bits of header where 0 < h < 1. Assuming ts setup time, how long does it take to send the packet?

    b. Suppose that the network is a circuit-switched network. Furthermore, suppose that the transmission rate of the circuit between source and destination is R/24 bps. Assuming ts setup time and no bits of header appended to the packet, how long does it take to send the packet?

    c. When is the delay longer for packet switching than for circuit switching assuming h=0.5. Interpret your result?